Re: CD recording


Subject: Re: CD recording
From: macCormac (macCormac@shaw.ca)
Date: Thu Sep 23 2004 - 10:29:28 EDT


NO NO my dear Mr Smalridge

it is U that are 2 kind and most humble. and ain't DAT th best sign o a
Genius at Work / Study / Playing Violin or other such string theories . .
.

Just don't forget ur flyin goggles ;-) now, please do pass th tea. would
you care fir a biscuit with your saran wrap ?

best, macCormac (any cousin o grover / oscar is a cousin o mine)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://www.sylvi.ca / na / da / bc / siwash rock & soundscape /
out back with th butterflies testing th relativity of th strang
theori/praxis
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subject: [7-5] How long do CD-Rs and CD-RWs last?
(2004/04/22)

CD-RWs are expected to last about 25 years under ideal conditions (i.e. you
write it once and then leave it alone). Repeated rewrites will accelerate
this. In general, CD-RW
media isn't recommended for long-term backups or archives of valuable data.

The rest of this section applies to CD-R.

The manufacturers claim 75 years (cyanine dye, used in "green" discs), 100
years (phthalocyanine dye, used in "gold" discs), or even 200 years
("advanced" phthalocyanine
dye, used in "platinum" discs) once the disc has been written. The shelf
life of an unrecorded disc has been estimated at between 5 and 10 years.
There is no standard
agreed-upon way to test discs for lifetime viability. Accelerated aging
tests have been done, but they may not provide a meaningful analogue to
real-world aging.

Exposing the disc to excessive heat, humidity, or to direct sunlight will
greatly reduce the lifetime. In general, CD-Rs are far less tolerant of
environmental conditions than
pressed CDs, and should be treated with greater care. The easiest way to
make a CD-R unusable is to scratch the top surface. Find a CD-R you don't
want anymore, and try
to scratch the top (label side) with your fingernail, a ballpoint pen, a
paper clip, and anything else you have handy. The results may surprise you.

Keep them in a cool, dark, dry place, and they will probably live longer
than you do (emphasis on "probably"). Some newsgroup reports have
complained of discs becoming
unreadable in as little as three years, but without knowing how the discs
were handled and stored such anecdotes are useless. Try to keep a little
perspective on the situation:
a disc that degrades very little over 100 years is useless if it can't be
read in your CD-ROM drive today.

One user reported that very inexpensive CD-Rs deteriorated in a mere six
weeks, despite careful storage. Some discs are better than others.

An interesting article by Fred Langa (of http://www.langa.com/) on
http://www.informationweek.com/story/showArticle.jhtml?articleID=15800263&pgno=1
describes how
to detect bad discs, and discusses whether putting an adhesive label on the
disc causes them to fail more quickly.

By some estimates, pressed CD-ROMs may only last for 10 to 25 years,
because the aluminum reflective layer starts to corrode after a while.

One user was told by Blaupunkt that CD-R discs shouldn't be left in car CD
players, because if it gets too hot in the car the CD-R will emit a gas
that can blind the laser
optics. However, CD-Rs are constructed much the same way and with mostly
the same materials as pressed CDs, and the temperatures required to cause
such an emission
from the materials that are exposed would melt much of the car's interior.
The dye layer is sealed into the disc, and should not present any danger to
drive optics even if
overheated. Even so, leaving a CD-R in a hot car isn't good for the disc,
and will probably shorten its useful life.

See also http://www.cd-info.com/CDIC/Technology/CD-R/Media/Longevity.html,
especially http://www.cd-info.com/CDIC/Industry/news/media-chronology.html
about
some inaccurate reporting in the news media.

See "Do gold CD-R discs have better longevity than green discs?" on
http://www.mscience.com/faq53.html.

http://www.loc.gov/preserv/study%20of%20CD%20longevity.pdf is a USA Library
of Congress study on longevity of CDs, including CD-R and CD-RW.

http://www.cdpage.com/dstuff/BobDana296.html has a very readable
description of CD-R media error testing that leaves you with a numb sense
of amazement that CD-Rs
work at all. It also explains the errors that come out of MSCDEX and what
the dreaded E32 error means to a CD stamper. Highly recommended.

An interesting document entitled "Care and Handling for the Preservation of
CDs and DVDs - A Guide for Librarians and Archivists" can be found on the
National Institute of
Standards and Technology (NIST) web site at
http://www.itl.nist.gov/div895/carefordisc/disc_care/. It has a wealth of
information about disc composition and longevity, as
well as recommendations for extending the lifespan of your media. (A
printable PDF can be found at
http://www.itl.nist.gov/div895/carefordisc/CDandDVDCareandHandlingGuide.pdf.)

Kodak has some interesting information about their "Ultima" media. See
http://www.kodak.com/global/en/service/cdrMedia/index.jhtml, specifically
the "KODAK Ultima
Lifetime Discussion" and "KODAK Ultima Lifetime Calculation" white papers
(currently in PDF format). The last page discusses the Arrhenius equation,
which is used in
chemistry to calculate the effect of temperature on reaction rates. The
Kodak page defines it as:

              t = A * exp(E/kT)

where 'exp()' indicates exponentiation. 't' is disc lifetime, 'A' is a time
constant, 'E' is activation energy, 'k' is Boltzmann's constant, and 'T' is
absolute temperature. The
equation allows lifetime determined at one temperature to be used to
establish the lifetime at another. If a disc breaks down in three months in
extreme heat, you can
extrapolate the lifetime at room temperature.

The trouble with the equation is that you have to know either 'A' or 'E'.
It appears that 'A' can be estimated based on empirical evidence, but see
http://palimpsest.stanford.edu/byorg/abbey/an/an23/an23-3/an23-308.html for
some cautions about how tricky it can be to choose the right value.

Jason Smalridge wrote:

> U R 2 Kind,
> I am but a humble servant to the gods of sound.
> May they bless us all with long lasting CD-R's (cool-dark-dry places,
> don't touch the shinny side- even if it is ever so inviting).
>
> Jay
>
> On 23-Sep-04, at 10:02 AM, macCormac wrote:
>
> > u r kidding ;-) it helps in NO small way, but helps alot. this site is
> > awesome for info . . .
> >
> > DR SMALRIDGE is a big man and rocks with th best o em :-)
> >
> > this is a great site. keep em coming with th INFO / MUSIQUE /
> > COM.MUNICATION
> >
> > and very very very dab (oswaldianmetaphorik) humour :-) est qe c'est
> > trés
> > bon for th soul music . . .
> >
> > pest, silly macCormac (canadienne goose)
> >
> > Jason Smalridge wrote:
> >
> >> Hi- lo,
> >> Try here to start with:
> >> http://www.cdrfaq.org/faq07.html#S7-5
> >>
> >> It's a hefty site but there is a lot of info on CD and recordable
> >> media.
> >> Hope it helps a little...
> >>
> >> Jay
> >> On 23-Sep-04, at 9:26 AM, macCormac wrote:
> >>
> >>> hey hey Mr In a Daze (aka Dr @ Small Ridge on th Edge o th
> >>> Laurentians
> >>> North Quest o Walden's Pond)
> >>>
> >>> i knew you were t/here with this cool post. wow this info is good.
> >>> thanks.
> >>>
> >>> am i slow ? waht iz th where iz the question. i'm scrooling /
> >>> drooling
> >>> to find.
> >>>
> >>> can you post th direct link-age for us old ladies with frock and
> >>> socks
> >>> ?
> >>>
> >>> yours sincerely, macCormac / sylvi (dis-abled in vaudeville ;-)
> >>>
> >>> Jason Smalridge wrote:
> >>>
> >>>> I think this may help to answer your questions.
> >>>> http://www.cdrfaq.org/
> >>>>
> >>>> Jay
> >>>> On 22-Sep-04, at 5:34 PM, Coryn Smethurst wrote:
> >>>>
> >>>> HHB audio guarantee their CDR's to last longer than 5 years,
> >>>> can't remember how long off the top of my head ...
> >>>>
> >>>> crrs
> >>>>
> >>>> on 22/9/04 20:13, Andres Lewin at alero@eresmas.net wrote:
> >>>>
> >>>> I am asking about experience on life of recorded CD-R.
> >>>> I am having trouble playing and saving material recorded on
> >>>> CD-R
> >>>> about 4-5 years ago. Beginning sectors mainly ok, but further
> >>>> progress in the CD noises appear. Once you extract it, the
> >>>> extraction
> >>>> time increases notably, and if you inspect the .wav files you may
> >>>> find clics or even empty spaces.
> >>>> Two days ago a composer residing in France made following
> >>>> statement as per his knowledge gathered at different electronic
> >>>> music
> >>>> studios.
> >>>> - Commercial released CDs: estimated life 20 years
> >>>> - recorded CD-R: estimated life 5 years
> >>>> Any body can give any light on this issue?
> >>>> Andres Lewin-Richter
> >>>> Phonos Foundation
> >>>> Barcelona
> >>>
> >



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